1. Field of the Invention
The present invention belongs to a technical field of manufacturing process of a semiconductor device, especially relating to a substrate processing apparatus performing a heating process onto a material used for forming an insulation film coated on the surface of a semiconductor wafer.
2. Description of the Related Art
In a manufacturing step in a process of a semiconductor device, for example, SOD (Spin on Dielectric) system is used for forming an inter-layer insulation film. In the SOD system, a coating film is spin-coated on a wafer with using sol-gel method and the like and an inter-layer insulation film is formed with performing processes like a chemical process or a heating process on the wafer.
For example, in a case of forming an inter-layer insulation film with sol-gel method, first of all, a material used for forming an insulation film, for example, a solution in which colloid of TEOS (Tetra-Ethyl-Orso-Silicate) is dispersed into an organic solvent is supplied on the semiconductor wafer (hereinafter referred to as a “wafer”). Next a gelling process is performed on the wafer on which the solution is supplied and subsequently solvent is being substituted. Then the heating process is performed on the wafer which solvent is being substituted, followed by a cooling process.
A series of steps such as applying an isolation film material, performing a gelling process, the heating and the cooling process, is done in a single processing system including a transfer mechanism transferring the substrate to each of the processing apparatuses.
Incidentally, in a step of heating process, for example, the heating process is being performed in a state of reduced pressure in the hermetically sealed chamber. Alternatively, the heating process is also being performed with decreased oxygen density in the chamber by introducing nitrogen as an inert gas thereto in order to prevent oxidation of the substrate.
However, especially when transferring the substrate into the chamber with the transfer mechanism, the substrate may be oxidized for it more or less has a moment of being exposed to oxygen. In addition, the turbulence in a flow of the inert gas when transferring the substrate in and out of the chamber may have a bad effect on the coated film.
In addition, a conventional method of introducing nitrogen to inside the chamber is generally aimed at the surface of the substrate, and there is a case that the nitrogen does not reach to a rear side of the substrate. For this reason, there is a problem that the conventional method causes oxidation on the rear side of the substrate.